On Sep 10, 2017, at 20:08, Nathaniel Smith <n...@pobox.com> wrote: > > I've sometimes wished that attrs let me control whether it generated equality > methods (eq/ne/hash) separately from ordering methods (lt/gt/...). Maybe the > cmp= argument should take an enum with options none/equality-only/full?
I have had use cases where I needed equality comparisons but not ordered
comparisons, so I’m in favor of the option to split them. (atm, I can’t bring
up a specific case, but it’s not uncommon.)
Given that you only want to support the three states that Nathaniel describes,
I think an enum makes the most sense, and it certainly would read well. I.e.
there’s no sense in supporting the ordered comparisons and not equality, so
that’s not a state that needs to be represented.
I’d make one other suggestion here: please let’s not call the keyword `cmp`.
That’s reminiscent of Python 2’s `cmp` built-in, which of course doesn’t exist
in Python 3. Using `cmp` is just an unnecessarily obfuscating abbreviation.
I’d suggest just `compare` with an enum like so:
enum Compare(enum.Enum):
none = 1
unordered = 2
ordered = 3
One thing I can’t avoid is DRY:
from dataclasses import Compare, dataclass
@dataclass(compare=Compare.unordered)
class Foo:
# …
Maybe exposing the enum items in the module namespace?
——dataclasses/__init__.py-----
from enum import Enum
class Compare(Enum):
none = 1
unordered = 2
ordered =3
none = Compare.none
unordered = Compare.unordered
ordered = Compare.ordered
——dataclasses/__init__.py-----
from dataclasses import dataclass, unordered
@dataclass(compare=unordered)
class Foo:
# …
Cheers,
-Barry
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